Study procedures
A complete medical history, physical examination, 12-lead ECG, chest x-ray and transthoracic echocardiogram were performed in each patient. Echocardiographic studies were performed in accordance with American Society of Echocardiography criteria. Left ventricular ejection fraction was measured using Simpson's rule in the apical four-chamber view. All measurements were performed during six cardiac cycles and averaged to account for beat-to-beat variation due to the arrhythmia. Echocardiographic values required a consensus of two experienced echocardiographers. The CHA2DS2VASc score,9 a clinical prediction rule for estimating the risk of stroke in patients with non-rheumatic AF, was calculated for each patient.